TT #189 · Parshas Tazria · Aliyah 5 · Passuk 30
English: the priest shall examine the affliction. If its appearance is deeper than the skin and it contains thin yellow hair, the priest shall pronounce him unclean; it is a netek, tzaraas of the head or beard.
Chabad.org — Chumash, English translation + Rashi for Vayikra 13:30
Torah Temimah cites Sifra (Toras Kohanim) for including appearances level with or higher than the skin, not only visibly depressed ones.
Sifra — Vayikra 13, Midrash Sefer
English: Although the verse calls the appearance “deep,” the Sifra includes an appearance level with the skin or raised above it, not only one visibly lower than the surrounding skin.
Textual derivation
“Deep” describes the visual impression associated with the lesion; it is not a requirement that the lesion physically sit below the skin surface.